Stand up for yourself
I am in a similar situation at my work. There is a senior dev and a group of "good old boys" that will put down others just for a laugh. It's not super malicious but annoying nonetheless.
Here is what has worked for me(YMMV):
Approach them directly, and ask them if they were talking to about you. If they admit they were talking about you be direct but non-confrontational. Say something like "I don't appreciate being mocked while at work. Please don't do that again. " I like this approach for a few reasons:
It shows them you will stand up for yourself.
Mentioning to a supervisor or HR, though justified, comes off as tattling.
It will make them somewhat uncomfortable facing the consequences of their actions. They should.
This may depend on the relationship with them. They may be reasonable and apologize. If you think you could get fired in retaliation, you may want to be careful. If they don't fess up that they were talking about you, apologize and move on. They may be lying, but at least they know that you will stand up for yourself.
It is sometimes uncomfortable to approach people directly about these kind of things, but I find that it is the most effective way of dealing with it.